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The “chiralisation” of Euclidean polygonal tessellations is a novel, recent method which has been used to design new auxetic metamaterials with complex topologies and improved geometric versatility over traditional chiral honeycombs. This paper aims to design and manufacture chiral honeycombs representative of four distinct classes of 2D Euclidean tessellations with hexagonal rotational symmetry using fused-deposition additive manufacturing and experimentally analysed the mechanical properties and failure modes of these metamaterials.

Finite Element simulations were also used to study the high-strain compressive performance of these systems under both periodic boundary conditions and realistic, finite conditions. Experimental uniaxial compressive loading tests were applied to additively manufactured prototypes and digital image correlation was used to measure the Poisson’s ratio and analyse the deformation behaviour of these systems.

The results obtained demonstrate that these systems have the ability to exhibit a wide range of Poisson’s ratios (positive, quasi-zero and negative values) and stiffnesses as well as unusual failure modes characterised by a sequential layer-by-layer collapse of specific, non-adjacent ligaments. These findings provide useful insights on the mechanical properties and deformation behaviours of this new class of metamaterials and indicate that these chiral honeycombs could potentially possess anomalous characteristics which are not commonly found in traditional chiral metamaterials based on regular monohedral tilings.

To the best of the authors’ knowledge, the authors have analysed for the first time the high strain behaviour and failure modes of chiral metamaterials based on Euclidean multi-polygonal tessellations.

Public schools operate in a changing and dynamic environment evident in technological innovations, increased social heterogeneity and competition, all contributing to school leaders’ uncertainty. Such changes inevitably influence schools’ inner dynamic and may therefore undermine schools’ organizational health. School leaders have a crucial role in buffering these external influences and promoting schools’ organizational health. The purpose of this paper is to assess the role transformational school leaders play in mediating the relationship between perceived environmental uncertainty and schools’ organizational health in a context characterized by uncertainty and instability which follow political instability.

The researchers administered questionnaires to 954 teachers coming from 191 randomly sampled public elementary schools in Israel.

Results indicate a negative impact that perceived environmental uncertainty has on schools’ organizational health evident in the degree of academic emphasis and staff affiliation with the school, in the school’s institutional integrity, and in the principal’s ability to both secure resources for the school and demonstrate collegiality toward teachers. Findings also show that transformational school principals are able to moderate the negative impact environmental uncertainty has on schools’ organizational health.

The findings validate the growing uncertainty characterizing the environment in which public schools operate. They further strengthen existing knowledge on the transformational leadership style in light of its unique capacity to buffer negative external influences imposed on schools and maintain their organizational health.